It is well known that phosphates and their salts are useful as emulsifying agents in the preparation of food products, for example, dairy products including process cheese. The preparation and properties of such emulsifying agents are well known. (See, U.S. Pat. Nos. 3,729,546 (Bell); 3,615,586 (Rohlfs) and German Patent Nos. 1,299,989, 1,692,305 and 2,342,299).
Sodium phosphates are commonly used in the manufacture of process cheese either alone or in mixtures. The sodium phosphates sequester calcium ions in the cheese, to solubilize the protein and increase its hydration and swelling, to facilitate emulsification of fat, and to adjust and stabilize pH. (See, Caric et al., Food Microstructure, Vol. 4, pp. 297 (1985). Sodium phosphates are of great importance to cheese processing because they affect the chemical, physical and microbiological properties of the finished cheese product. Sodium phosphates are not emulsifiers in the strict sense, i.e. they are not surface-active substances, yet they are commonly included in the group of ingredients called "emulsifying agents" (See Caric et al., Food Microstructure, Vol. 4, pgs. 297-312 (1985).
Process cheese is prepared by heating hard cheese and/or soft cheese in a mixture with certain emulsifying agents in a melting process to a temperature above about 80.degree. C. During this melting process, the insoluble starting cheeses are converted into liquid by means of the emulsifying agents. (See U.S. Pat. No. 3,615,586).
The known processes to prepare process cheese typically involve the addition of the sodium phosphate emulsifying agents as dry-solids or as a combination of concentrated solutions of disodium phosphate and trisodium phosphate from separate heated storage tanks. Problems are associated with these processes, however. Adding solid sources of sodium phosphates can result in a phosphate build up within a cooker or blender because the solid phosphates do not fully dissolve and stick to the augers. The build-up of phosphates on the inside of the cooker or blender causes the cheese to burn during the cooking cycle. Undissolved phosphates also give the processed cheese a lumpy consistency. Furthermore, when a solid source of sodium phosphate does not fully dissolve in the process mixture, the residual undissolved solid sodium phosphate contributes to the solids that are removed by filters.
Alternatively, if concentrated liquid sources of disodium phosphate and trisodium phosphate are utilized in the cheese manufacturing process, these solutions must be stored at elevated temperatures (130.degree. to 160.degree. F.) to prevent crystallization of the sodium phosphates from solution. Storing the concentrated disodium phosphate and trisodium phosphate solutions at elevated temperatures requires expensive insulating and heating equipment which increases manufacturing costs significantly. Furthermore, if a malfunction allows the temperature to drop, the solutions can crystallize within the delivery system, resulting in expensive downtime, repairs and/or replacement of the tanks, pumps, valves and piping.
Further, the manufacture of dry disodium phosphate, can result in pyrophosphate formation resulting from two disodium phosphate molecules fusing together. This is caused by high temperatures (approximately 450.degree. C.) in the drying process. Pyrophosphate contamination in the process cheese will result in the failure of starting cheeses to completely homogenize. (See, Molins, Phosphates in Food, CRC Press Inc. (1991) pg. 57). As much as 0.5% tetrasodium pyrophosphate in the disodium phosphate is detrimental to its use in process cheese. Toy, Arthur D. F., Phosphorus Chemistry in Everyday Living, A.C.S., Washington, D.C., 1976. The processed cheese would lose its melting properties.
The addition of dry solid sources of disodium phosphate and trisodium phosphate requires human labor to physically add the appropriate amount of the disodium phosphate and/or trisodium phosphate. This results in substantial bag disposal cost, phosphorous additions to landfills, and occasionally, human error in measuring the amount of phosphate to be added. Injuries from lifting heavy bags are also a concern for employees and employers.
For these reasons, the preparation of process cheese using a dry solid source of sodium phosphates or by adding separate amounts of concentrated disodium phosphate or trisodium phosphate solutions stored at elevated temperatures is an expensive process. The use of the solid has the same disadvantages as mentioned above for processing cheese. Also, the use of liquid trisodium phosphate would require heated storage and steam traced piping.
Trisodium phosphate is also used in other food processing industries such as meats, fish and poultry for reducing, removing, retarding or controlling salmonella and other spoilage bacteria. (See U.S. Pat. Nos. 5,192,570; 5,143,739; 5,069,922; 5,262,186; 5,268,185; and 5,283,073). Thus, it is an object of this invention to prepare food products by a more economic and quality concerned route.